Luke's character would become much more complex. He would likely start to show more aggression and a lack of mercy. His once - bright eyes might become clouded with darkness. For example, he could start using the Force in cruel ways, like choking his enemies without hesitation as Vader did.
Luke's appearance might also change. In the Star Wars lore, those who embrace the Dark Side sometimes have a more menacing look. His robes could become darker, his hair might look more unkempt, and there could be a constant scowl on his face. His transformation would not just be physical but also mental and emotional, making him a very different character from the one we know in the original Star Wars story.
If Luke joins the Dark Side, it would completely change the dynamic of the Star Wars universe. His friends would be shocked and heartbroken. Leia, for instance, would probably try to bring him back. The Rebellion would lose a great hope and the Empire might gain an unexpected and powerful ally. It could also lead to a different kind of struggle within the galaxy as those who once believed in Luke now have to face him as an enemy.
She would become more ruthless. Instead of being the hopeful and somewhat naive Rey we know, she would be calculating. For example, she might not hesitate to sacrifice a few for the sake of what she believes is a greater good. Her appearance would also change. Maybe she would start to dress in darker colors, and her eyes could take on a more menacing look. Her relationships would be different too. She would probably break off ties with her old friends from the Light Side, seeing them as obstacles to her new goals.
This would be a huge twist. It might mean Luke is seduced by the dark side's power or has some ulterior motive for joining Vader. It could change the course of the entire story.
Not as far as I know. Luke has typically remained on the side of light in the Star Wars comics.
In the fanfiction, Luke could be influenced by his family ties to the dark side. If he discovers some hidden connection to Vader or Palpatine that he didn't know before, it might make him question his place on the light side. He could think that joining the dark side is a way to understand his true heritage better and gain more power to protect those he loves in a different way than the Jedi would allow.
It could be the remaining Jedi. Since Luke is turning to the dark side, the Jedi who still uphold the light side values would be against him. They would see him as a threat to the balance they are trying to maintain and would try to stop him from fully embracing the dark side.
A plot twist could be that Rey has a dark heritage she was unaware of. When she discovers this, she feels a pull towards the Dark Side. She may struggle with this newfound knowledge at first, but eventually give in. In the story, her transition to the Dark Side could cause chaos in the Star Wars universe. The Resistance would be shocked and some might try to bring her back. However, the Dark Side could give her new powers and a different perspective on the Force. She could then start to reshape the Sith ideology, creating a new form of the Dark Side that is more in line with her own beliefs, leading to a whole new conflict in the galaxy.
The power balance would be severely disrupted. The Rebellion would lose one of its most important leaders, and the Empire or any other dark side - aligned forces would gain a significant advantage. Her knowledge of the Rebellion's strategies and bases could be used against them.
It could be a new Sith Lord created specifically for the fanfiction. This new character could be more powerful and devious than any before. He could be the one who lures Luke to the Dark Side and then becomes his enemy as they compete for power within the Dark Side hierarchy.
Another plot could involve a powerful Sith Lord who manipulates Luke. The Sith Lord could use Luke's insecurities, like his fear of not being strong enough to protect his friends. He could be tricked into believing that the Dark Side would give him the power he needs, and slowly turn to the dark side as a result.